The present invention relates to a mine roof support, and more particularly to a shield mine roof support.
It is known to work in a mine face by a peeling or cutting mining device which reciprocates in longitudinal direction of a gallery on longitudinal guides. The removed mineral is conveyed directly from the mining device or from loading arrangement coupled with a mining device, to a continuous conveyor displaceable along the mine face. Then the mineral is delivered to a further conveying arrangement which moves in a mine face gallery at the end side of the first-mentioned gallery.
In connection with this, it is further known to hold open the excavated gallery space, that is so called travel field and conveying field, by shield mine roof supports located adjacent to one another in longitudinal direction of the gallery. Each of the mine roof supports has two sole sliding elements or skis, and a breakage shield-roof supporting arrangement which is supported on the sliding elements by props. The known mine roof support further has a guiding arrangement arranged between the sole sliding elements and including two laterally spaced guiding rods which are connected at their mine face end with a conveyor. The guiding rods are also connected at their backfilling ends with a bridge connecting the mine face ends of the sliding elements, via a displacing arrangement extending toward the mine face. The displacing arrangement in the known mine roof support is formed by a hydraulically actuated cylinder-and-piston unit with a cylinder articulately connected to the bridge and a piston articulately connected to the guiding arrangement. In such a construction the great piston faces of the cylinder-end-piston unit can be utilized for advancing the mine roof support in direction toward the mine face.
The stroke of the displacing arrangement is so selected that the conveyor can be displaced in one or several steps in correspondence with the cutting depths of the respective mining device to follow the mine face, by actuating of the annular face of the cylinder-and-piston unit. When the stroke of the displacement arrangement comes to the end, the mine roof support moves back with abutment against the conveyor.
The cutting depth of a planing mining device amounts only to several centimeter. The cutting depth of the conventionally 2-roller cutting mining arrangement reciprocable relative to the mine face also does not exceed 1 meter. As a result of this, the cylinder-and-piston unit of the displacing arrangement which advances the conveyor or displaces the mine roof support has, in condition of sufficient length, a diameter which corresponds to the mine dimensions. Furthermore, it is known to work in a mine face with the utilization of a generally self-propelling guide-free mining device which is provided at its end face with vertical raisable and lowerable material-removing drum. The latter has as a rule a length of several meters and attains in the mining field a coal-excavating depth which is a multiple of the cutting depth of the reciprocable cutting machine. The mine field to be worked is subdivided by transverse and longitudinal cuts into a plurality of working locations which are worked one after the other or simultaneously whereby several uprights for supporting the mine structure remain spared. In this case one must consciously accept the loss of greater coal quantities which must be retained as supporting uprights because the utilization of working mine roof supports, particularly shield mine roof supports, in condition of mining with such great excavation depths has not been successive. This is because the cylinder-and-piston unit of the displacing means in condition of mine dimensions cannot be formed so long as to cover, as compared with the known planing or cutting methods, a multiple great coal excavating depths with respect to the advancement of the conveyor or the return of the mine roof support.